The present invention relates to motion vector estimation in video images. Particularly, but not exclusively, it relates to motion vector estimation for standard conversion.
Motion vectors are used, for example, to estimate the position a (generally very small) part of the video image would occupy in a field to be interpolated between two input fields. The process may take place at the transmitting and/or at the receiving end and the part of the picture, herein referred to as a block, may be as small as a single pixel or may comprise a plurality of pixels adjacent to one another. In general, for a given block, a prediction vector, for example the motion vector from a previous block, is provided and a search is made around the predicted area in the second field to find the best match of pixel values over a block in the second field with that of the block on the first field. Such a system, with component based recursion is described in the article "New Algorithm for Motion Estimation" by Gerard de Haan and Henk Huijgen, Proceedings of the Third International Workshop on HDTV, Torino, 1989 sponsored by the IEEE, SMPTE et al. The article also includes a two-directional convergence scheme. The contents of the article will be reviewed in greater detail below, but the system it proposes has a limited search area and yields a stable estimate, but the convergence speed can be improved.